The Sony X111ES has headphone outs, so my Dad was arguing that plugging in headphones directly from the source would provide the best listening experience.

But my argument was that going from the Sony> -- NAD 1600 --> headphones would be better

I have very little knowledge of 'the science' of what goes on inside equipment (receivers, sources, amps, headphones). So if anyone could answer just who is correct and with a scientific explanation, that would be great. If anyone doesn't mind, I'd love a long, lengthy reason.

The Sony X111ES has headphone outs, so my Dad was arguing that plugging in headphones directly from the source would provide the best listening experience.

But my argument was that going from the Sony> -- NAD 1600 --> headphones would be better

I have very little knowledge of 'the science' of what goes on inside equipment (receivers, sources, amps, headphones). So if anyone could answer just who is correct and with a scientific explanation, that would be great. If anyone doesn't mind, I'd love a long, lengthy reason.

Thanks!

Can't find the output impedance of the Sony.

The NAD phone jack has an output impedance of 120 ohms.

What headphones are you using?

Most people would agree that a headphone jack with a low output impedance is better, say 10 ohms.

I'm unfamiliar with this gear. When connecting the X111ES to the NAD 1600, it's an analog connection (already been through digital-to-analog) or digital?

What matters is the circuitry powering the headphones (headphone amplifier) and the circuitry doing the digital-to-analog conversion. The goal of the headphone amplifier is to take the input it gets and output that same signal (maybe scaled higher or lower, but same shape) to the headphones it's connected to. Since headphones have relatively low impedance in electronics terms, they present a nontrivial load to the headphone amplifier, requiring some decent current. How much depends on the output level and the headphones. However, no amplifier is perfect and can exactly duplicate the input. Different headphones amplifiers will deviate in different ways, by different amounts, at different frequencies, into different headphones. The performance is determined primarily by the design of the electronics, partly by which components are used for that design, and so on. That's complicated.

Similar things can be said about the digital-to-analog process. Nothing can do that perfectly either. But note that both the headphone amplifier and digital-to-analog can be done so well as to make an inaudible difference to human hearing and perception, but this isn't always the case.

By plugging into the NAD 1600, you're using that device's headphone amplifier rather than the X111ES's headphone amplifier. If the NAD 1600 has a better headphone amplifier (to your ears, for those headphones, at that listening level), then that will be superior. If the X111ES has a better headphone amplifier, then that will be better.

I have very little knowledge of 'the science' of what goes on inside equipment (receivers, sources, amps, headphones). So if anyone could answer just who is correct and with a scientific explanation, that would be great. If anyone doesn't mind, I'd love a long, lengthy reason.

Thanks!

Here's your long, lengthy scientific explanation:

paraphrased from another thread:

From a pure electrical engineering point of view, it is pretty cut and dried:

- virtually no frequency response interactions between the heaphone and the headphone amp impedances (this really only applies to headphones with a varying impedance WRT frequency (for example, DT880/32 ohm))

- improved efficiency between the amp and the headphone; when you are driving a 120 ohm headphone with an amp with a 120 ohm output impedance then you are wasting half the amplifier output power, obviously this gets important when driving low impedance 'phones from a high output impedance headphone jack

as I said earlier, your NAD has an output impedance of 120 ohms

I don't know the output impedance of the Sony, I couldn't find it on the 'net so I can't comment on it

the Sennheiser HD600 have an impedance of 300 ohms or more, they will be OK with the NAD

the AKG 240 have an impedance of 50 ohms or more, they may sound rather boomy and distorted out of the NAD